Hydraulically operable valve actuators of a range of forms are well known. One known form of actuator comprises a piston movable within a cylinder, the piston being spring biased towards one position, and being movable to another position upon the application of fluid under pressure to a chamber of the cylinder. It will be appreciated that by coupling a valve member of an associated valve to the piston, movement of the piston can result in accompanying movement of the valve member, opening or closing the valve.
In order to provide a visible indication of the valve position, it is known to provide the piston with a rod movable therewith, the rod carrying a spring abutment member with which the biasing spring engages to bias the piston towards the rest position mentioned hereinbefore. One or more indicator pins are rigidly secured to the spring abutment member, the pins extending through openings formed in a housing. As the pins are rigidly secured to the spring abutment member which moves with the rod and piston, it will be appreciated that the distance by which the pins project from the housing at any given time provide an indication of the position of the actuator and valve at that time.
Whilst the arrangement described hereinbefore permits an indication to be made of the valve position, assembly of the actuator is time consuming as the spring abutment member must be accurately positioned in order to ensure that the pins align with the openings formed in the housing. Slight misalignment therebetween may impede movement of the spring abutment member and/or result in increased wear or leakage past the pins and seals located between the pins and the housing.